A wide range of systems and methods are currently popular for the drainage of body fluids in the field of medicine. In all those cases in which body fluids are drained and collected by the use of vacuum, this can, for example, take the form of a rigid collection vessel fitted with a cap into which, a) the drainage tube is led and, b) a connection is provided for vacuum. This connection is linked to a source of suction, such as a suction pump. The problem inherent in this type of system according to the prior art is the fact that the collection vessel has to be transported in its entirety in order to dispose of the fluids collected and, after the contents have been emptied out, this same collection vessel must be carefully cleaned. According to the current state of information, this type of system no longer fulfills the demands made on hygiene in certain cases. In order to solve this problem, it was proposed to fit a disposable bag inside the rigid vessel for the sole purpose of collecting the fluids being drained off. As described, a bag filled with fluid can be disconnected from the cap of the vessel and removed for disposal at the designated disposal point while the rigid vessel can usually be fitted with a new bag. The problem inherent in this type of system is the fact that two different vacuum tubes are required, these being one to open the bag and pull it against the inner wall of the vessel and a second connection to the inside of the bag in order to produce the required vacuum within the bag after the latter has been expanded. Care must always be taken to ensure that the vacuum in the space surrounding the bag is greater than that inside the bag as there is otherwise a danger of the bag collapsing again and preventing any further filling. Apart from these problems, a design of this type is complicated and thus expensive.